Crystallographic insights into the role of nickel on hardenability of wear-resistant steels

•Revealing the role of nickel on hardenability by visualization and digitization of variants.•Increased nickel modified the variant paired mode and enhanced the hardenability.•Variant paired mode shifted from Bain grouping to CP grouping by increased nickel.•Microstructure with high density of block boundaries contributed to high hardness.•Increasing nickel content promoted to form high density of block boundaries.